cornea human

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cornea human

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  • CORNEA

  • Dr.H.Izar Aziz,SpM(K)*Function of the cornea :as Window of the globe & refractive media:clear & transparent with power + 42 D.as microorganisms barrier

    Dr.H.Izar Aziz,SpM(K)

  • Corneal endothelium maintains corneal clarity through:Acting as a barrier to the aqueous humorProviding metabolic pump*Loss of transparency caused by : endothelial damage epithelial damage.

  • Corneal EdemaAlteration of endothelial function corneal edemaAcute altered barier effect of the endothelium/epitheliumChronic inadequate endothelial pump*

  • Causes of Corneal EdemaAcuteTrauma (ex: intraocular surgery)Inflammation Hypoxia (ex: contact lens wear)Increased intraocular pressureChronicTrauma or toxinsFuchs dystrophyPosterior polymorphous dystrophyIridocorneal endothelial syndromeRetained lens fragment*

  • *Keratitis : isinflammation of cornea ,caused bymicroorganism infectionantigen antibodies / allergic reaction.

  • *Epithelium covered by tear film :as a barrier microorganisms infection . (except N. Gonorrhoea)Descemets membrane as barrier for bacterial infection to COA .(but not for fungus)

    Etiology of keratitis : Exogenous : bacteria ,fungus , virus, parasiteEndogenous : allergic reaction.

  • *Bacteria :-Pure Pathogen : Streptococcus pneumoniae, Pseudomonas aeroginosa

    -Opportunistic bacteria : -Staphylococcus,Moraxella, Serratia(as flora at conjunctiva

    . Alcoholic/ B6 deficiency .Topical steroid >>>. Corneal abrasion Pathogen bacteria Corneal infection

  • *Fungus (usually opportunistic)Candida, Fusarium, AspergillusVirusVHSVVZParasite : Acanthamoeba in Contact lens user

  • *Symptoms & SignsSubjective (patients history )painglare (photophobia)blur vision tearing (lacrimation)

    Objective - loupe or slit lamp examinationblepharospasmeciliary injection tearing (lacrimation)superficial infiltrate or corneal ulcer hypopyon- in advanced cases.

  • *

  • *Special examinations : Flourescein test for corneal ulcer Seidel test for perforating cornea

  • *Laboratory Studies Etiologic diagnosis.Scraping from:infiltrate / edge of the ulcerfornices of conyunctivaSlide Staining :Gram ( for bacteria)Giemsa (for fungus )

  • *Clinical courseSubepithelial /epithelial keratitisRecover without scar Become corneal ulcerCorneal blindnessrecoverExtirpation of the globeAbulbi Phtysis bulbiPermanent blindness

  • *Clinical appearance of corneal ulcersSerpeginous corneal ulcer.Etiology : Pneumococcusacute, well circumscribed gray ulcer, tends to spread to center of corneahypopyon is common (sterile)

  • *Pseudomonas ulcer. Etiology : Pseudomonas aerg. (present in Flourescein sol.) bluish-green exudate very acute ,spread rapidly to all direction ,because proteolytic enzyme destroy the corneal stromadescemetocele

  • *Marginal Ulcer Etiology : Staphylococcusaffect limbal area Fungal ulcerhistory: agriculture trauma topical steroid usage >>>>gray Infiltratethick hypopyon & irregular surfacesatellite lesions - in endothelium

  • *Herpes Simplex keratitis.Etiology : VHS type Icorneal sensibility
  • *Moorens UlcerEtiology : antigen antibodies reactionProgressive excavation of the limbus.

  • *Treatment atropine eye drops Anti microorganisms depend on laboratory finding (scraping & culture) Antibiotic for bacteriaAnti fungus for fungal infectionAntiviral for viral infectionSteroid for Moorens ulcereye bandage

  • *Prognosis depends on :depth & width of the ulcer Corneal scar

  • Dr.H.Izar Aziz,SpM(K)*NebulaMakulaLeukomaLeukoma adherentCentral ,-->corneal blindness-Periphery (No visual disturbance )

    Dr.H.Izar Aziz,SpM(K)

  • Dr.H.Izar Aziz,SpM(K)*PreventionAvoid corneal traumaAvoid overuse of topical steroid Cure external eye infection as soon as possible.Avoid trigger factor for relapsing H.simplex keratitis.

    Dr.H.Izar Aziz,SpM(K)

  • KeratoconusA progressive thinning and bulging of the central of paracentral cornea cone shape cornea6-8% cases: positive family historyOnset: around puberty

  • Clinical Findings Unilateral High astigmatism and myopic blurred visionMunson sign: bulging of the lower lid in downgaze

  • Treatment SpectaclesRigid contact lens Keratoplasty

  • *Reference BooksVaughn D, Asbury T; General Ophthalmology, 15th edition, Appleton & LangeMiller S; Parsons Diseases of the eye, 17 th Edition, Churcill Livingstone, 1984Kanski JJ, Clinical Ophthalmology, 4th edition,Oxford Butter Worth Heineman Ltd, 1999

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